The identification means of work pieces utilized for its identification and traceability throughout the manufacturing process and product life cycle has become a necessity for the high productivity required by the increasingly competitive global manufacturing operations having multiple part variants within a products' family, using multiple work-piece part work holding fixtures, and at multiple manufacturing locations, being produced via sequential machining-manufacturing operations, and manufacturing processes. As the work-piece part's identification data is frequently required by the Manufacturer's Quality Plan, Industrial Standards Organizations, Regulatory Agencies, customer(s) specifications, etc., such as for patient specific replacement(s), the work-piece part's design revisions, the product's assembly of multiple work-piece parts having a combined tolerance stack-up, a work-piece part's/Article's certificate of origin, Department of Defense components, product recall campaigns, forensic identification, etc.
Traditional Direct Part Marking Via the Manual Direct Work-Piece Marking and Identification Via Impacting Stamps
Manual work-piece direct part marking may not be desirable, and or suitable, for most modern manufacturing processes. Because it is susceptible to human error(s) for correctly marking the work-piece part/article, with errors negating the intended purpose of the work-piece parts'/articles' identification, and potentially injurious to personnel, via using a hammer to impact the hardened steel character forming stamp(s) onto the work piece's surface, to a semi-controlled depth, to indent and displace the surface material of the work-piece part/article to create a readable character and or symbol causing the displaced material to project above the previously smooth surface.
As a Secondary Operation Via the Semi-Automatic Direct Work-Piece Marking and Identification
Semi-automatic work-piece direct part marking can be done as a secondary operation to the primary manufacturing process that may not be desirable, and or suitable, for manufacturing processes that requires integrity of the data because it is susceptible to error(s) for correctly marking the corresponding work-piece part/article with the required data, with errors negating the intended purpose of the work-piece part's/article's identification.
Automatic Point-Of-Manufacture Work-Piece Marking and Identification
Automatic point-of-manufacture work-piece part/article engraving for marking/identification minimizes the opportunities for data error(s) and eliminates the potential for injuring personnel.
Automatic point-of-manufacture Work-piece Engraving is desirable at the point of manufacturing the work-piece part/article because of its being an integral operation of the production process to ensure the product's work-piece part/article marking and identification data integrity.
Automatic Work-piece Engraving is desirable to reduce the operator's potential for injury by eliminating the use of having to manually impact the hardened character forming stamp(s) against the work-piece part/article.
Existing Engraving Methods:
Currently, there are two common methodologies for Automatic point-of-manufacture direct work-piece marking spindle tooling used within Computer Numerically Controlled (CNC) Machine Tools, both having a different single point tool for either cutting material from the work-piece surface or impacting the work-piece part/article to indent and displace the work-piece part's/article's base material to create a readable character and or symbol:
Single Point Cutting Tools:
Cutting material from the work-piece surface using one rotating fluted cutting tool being plunged into the work-piece to a specific depth for the tool's cutting land(s) to remove the material from the work-piece surface while it's being moved parallel to the work-piece part's/article's surface by the motion of the CNC machine tool, to “write” the segments of a character via the removed material of the work piece's cutout profile cross section at specific location(s) and or along a path of lines and or curves on the work-piece part's surface to engrave a readable character and or symbol.
Single Point Impacting Tools:
Impacting via the “dot-peen” or scribing via the “Square-Dot” methodologies onto the work-piece part to indent and displace the work-piece material using a percussion motion to plunge a single point stylus into the work-piece to a depth to displace the material of the work piece's surface with the tool being lifted from the work-piece part's/article's surface as the tool is being moved parallel to the work-piece surface by the CNC machine tool to the next specific location(s) to “write” the character via the visually contiguous/adjacent pointed stylus at a specific location(s) or along a path of lines and or curves on the work-piece part's surface making a readable character and or symbol.
Multiple Point Impacting Tools:
Impacting the work-piece to indent and displace the work-piece material using a percussion motion to plunge multiple single point styluses into the work-piece to a depth to displace the material of the work piece's surface with the tool being lifted from the work-piece surface to “write” the next character via the visually contiguous/adjacent multiple pointed styluses impact “dots or dot-peen” at a specific location(s), or along a path of lines and or curves on the work-piece part's surface making a readable character and or symbol.
Disadvantages of the Existing Work-Piece Part Engraving Methods:
Both of the single stylus direct part marking processes described above have the same initial limitation for the Automatic point-of-manufacture work-piece direct part marking and identification operation, as that of being a time consuming operation for an expensive machine tool and manufacturing process via being constrained by their respective single point tooling for the work-piece part's surface material displacement.
The higher manufacturing costs and reduced tool life for the rotating Cutting tool method of engraving are comparable to the standard single point CNC cutting tools.
The Impacting pointed stylus direct part marking devices are more expensive and potentially damaging to the CNC machine tool's precision spindle bearings. While the smoothness of the work-piece surface is disrupted by the impacting of the pointed stylus potentially affecting its assembly to an adjacent work-piece part, while the displaced work-piece surface material can become a source of contamination in the application of the work-piece part(s) in its assembly.
Disadvantages of Marking Inks and Printed Labels:
The use of a “permanent” marking pens and inks to mark/identify the work-piece has multiple limitations such as:                A) The manual method of pen marking the readable character and or symbol to the corresponding work-piece part is subject to human operator error and the readers' interpretation of the data.        B) The marking ink may not adhere to the machined work-piece part's surface because of the machine tool's cutting fluid and or protective coating on the work-piece part.        C) The vibratory fluidic and or aggregate stone processes used to de-burr/remove the sharp edges of the machined work-piece part can also remove the marking ink from the work piece, requiring the remarking of the work-piece after its de-burring operation.        D) The agitated and or high pressure washing and rinsing processing operation(s) of the machined work-piece part can remove the marking ink from the work-piece part.        E) The corrosion resistant/preservative coating fluid used for storing and shipping the work-piece part can remove the marking ink from the work-piece part.        F) The marking ink may need to be removed from the work-piece part at the components' assembly point to prevent contamination of the assembled product.        G) The marking ink would not be readily detectable on the work-piece part beneath the assembled components' painted surface.        H) The initial marking ink's information prior to the machining operation may be critical to the documentation required for the traceability of the work-piece part and its data that may need to be captured before its removal from the work-piece part.        I) The marking ink's information after the machining operation may be critical to the documentation required for the traceability of the work-piece part and its data that may need to be captured before its removal from the work-piece part.        
The use of an adhesive backed printed label to mark/identify the work-piece has multiple limitations such as:                A) The manual application of the correct adhesive backed printed label to the corresponding work-piece part is subject to human operator error.        B) The adhesive backed printed label may not adhere to the machined work-piece part because of the machine tool's cutting fluid on the work-piece part.        C) The vibratory fluidic and or aggregate stone processes used to de-burr/remove the sharp edges of the machined work-piece part can also remove the adhesive backed printed label from the work-piece part.        D) The agitated and or high pressure washing and rinsing processing operation(s) of the machined work-piece part can also remove the adhesive backed printed label from the work-piece part.        E) The corrosion resistant/preservative coating fluid used for storing and shipping the work-piece part can remove the adhesive backed printed label from the work-piece part.        F) The adhesive backed printed label may need to be removed from the work-piece part for the assembly of the components as required to prevent contamination of the assembled product part.        G) The adhesive backed printed label may need to be removed from the work-piece part for the assembly of the components as required for the proper fit-up with the adjacent components.        H) The adhesive backed printed label may need to be removed from the work-piece part after the components' assembly to facilitate painting.        I) The adhesive backed printed label would not be readily detectable beneath the surface of the components' painted surface.        J) The initial printed label's information prior to the machining operation may be critical to the documentation required for the traceability of the work-piece part and its data that may need to be captured before its removal from the work-piece part.        K) The printed label's information after the machining operation may be critical to the documentation required for the traceability of the work-piece part and its data that may need to be captured before its removal from the work-piece part.        
Considerations for the productive machining of work piece parts and the increased necessity for the automatic point-of-manufacture Direct Work-piece Marking and Identification:
The automatic point-of-manufacture direct work-piece part marking operation is an additional machining operation that requires its minimization to reduce the CNC machine's overall cycle time to a minimum, as the cost basis for CNC Machining is a combination of cost effective equipment utilization, the quality, and the quantity of work-piece parts/articles being produced in the shortest time possible.                A. The higher quantity of work-piece parts increases the opportunities for manual work-piece part marking operation errors and operator injuries using impacting stamps.        B. The higher productivity of the high speed/high production output advanced machine tools' increases the opportunities for manufacturing defects via increasing the quantity of defective work-piece parts that could be produced in a shorter time span.        C. The higher productivity of machine tools increases the quantity of work-piece parts that need to be identified via the work-piece part marking operation of the manufacturing process.        D. The higher productivity of the high speed machining for advanced machine tools can be attributed to a combination of advances in (a) cutting tool technologies (materials, designs, & coatings) to facilitate rough machining in only one pass for the maximum work-piece material stock removal and then using the same cutting tool for the finishing pass for a “mirror like” surface finish or one pass for the maximum work-piece material stock removal and simultaneously producing a “mirror like” surface finish, (b) the higher speed computer processors, digital inputs, and outputs directly increasing the speed of the machine tools' driven axes and spindles, (c) the improved machine tool designs' utilization of full-time pressure lubricated recirculating bearings ways, ceramic elements, closed loop liquid temperature management, and thermal compensating algorithms to manage its heat generating mechanisms, (d) the machine tools' NC-Programming productivity simulation software and “chip thinning” machining methodologies being utilized to increase cutting feed rates within a tool's operational machining path, etc.        E. The high speed machining of multiple work-piece parts causes heating of the work-piece part that in turn causes dimensional changes from work-piece to work-piece over a period of time and or within a group of multiple work-piece parts being machined via the same machining cycle.        F. The machining of work pieces, especially at high speed, causes heating of the work-piece that causes dimensional changes from work-piece to work-piece over a period of time being caused by changing ambient and work-piece temperatures and the stress-relief/normalization caused by the removal of the raw work-piece material. This can necessitate the Coordinate Measurement Machine's dimensional inspection of the machined work-piece part being delayed, 22 hours or more for some applications.        G. The higher productivity of high speed machining increases the opportunities for manufacturing defects via increasing the thermal dimensional changes of the finished work pieces. These errors are corrected by the Coordinate Measurement Machine's dimensional inspection of the work-piece part(s) having been machined at a specific time and fixture location(s), then using the corresponding work piece's CMM inspection data for correcting the corresponding machine tools' work-piece part machining NC-Program as required. The improved high speed machining of aluminum work-piece parts has resulted in the machining cycle time for 4 parts being machined in one operation on 2 sides being reduced from 97 minutes when the manufacturing operations were developed in the 1990s, to 9:36 minutes in 2013 via the NC-Program O0602.        H. The dimensional changes of the finished work-piece part caused by thermal changes during machining can be combined with those caused by the stress-relief/normalization of the raw work-piece material that are then corrected by the Coordinate Measurement Machine's dimensional inspection of the work-piece part having been machined at a specific time and fixture location(s), then using the corresponding work piece's CMM inspection data for correcting the corresponding machine tools' work-piece part machining NC-Program as required. The improved high speed 6 sided machining of one cast iron work-piece part “317” has resulted in the machining cycle time being reduced from 390 minutes being done via 4 machining operations on a 4 work-piece part locating fixtures on 3 different CNC machines when the manufacturing process was developed in the 1990s, to 112 minutes on 2 work-piece part locating fixtures on 1 CNC machine in 2011 via the NC-Programs O3170, O3171, and O3173.        I. The specific work-piece part being sequentially machined at specific location(s) of a high density multiple position work-piece holding fixture need to be uniquely and correctly identified to facilitate that work-piece parts' correct sequential transfer to the next subsequent machining location(s) of the fixture and for the appropriate and corresponding corrective action(s).        J. The multiple sources and suppliers for the incoming raw work-piece parts to be machined increases the opportunities for manufacturing defects via the increasing variability of the raw work-piece parts coming from multiple casting patterns and or suppliers such as those having a specific date stamp identification for a specific group of raw work-piece parts and or having various suppliers for those work-piece parts.        K. Multiple work-piece parts having been potentially machined at numerous locations of a multiple position work-piece holding fixture, having the variables as in paragraph J above, will need to be uniquely and correctly identified to facilitate the corresponding work-piece parts' correlation to the specific machine tool(s) used for machining, the cutting tool(s) that were used, and the specific location(s) of the work holding fixture(s) for the corresponding corrective action(s) that may be required for that specific work-piece part.        L. The cell of multiple automatic machine tools, which includes the transferring of multiple pre-loaded work pieces pallets, and the machine tools' specific pre-installed initial and sometimes multiple backup tools that are automatically selected after the initial tools' specific operational usage limit is reached to facilitate automated manufacturing operations, relies on the tracking and serialization data of the work-piece parts for the traceability of defects and for the corresponding corrective action(s).        M. The automatic point-of-manufacture direct work-piece part marking/engraving operation within the machine tool becomes a portion of the machine's cycle time, increasing the machine's overall cycle time, and increases the machining cost of the work-piece part/article.        
However, the total manufacturing costs for the high productivity sequential machining of multiple work-piece parts will increase when the shorter cycle time of not marking the work-piece parts causes the erroneous sequential transferring of work-piece parts between the sequential machining operations and the increased difficulty for the root cause defect analysis and the corresponding corrective action required for eliminating defective and out of tolerance work pieces. The sequential machining of multiple work-piece parts, correctly via multiple operations, can be dependent upon using the same manual transfer sequence for the work-piece parts from one of the previous sequential work-piece parts' fixture location to the next sequential work-piece parts' fixture location for the next machining/manufacturing operation.